HPE FlexNetwork 7500 Switch Series

Transcription

1 HPE FlexNetwork 7500 Switch Series IP Multicast Configuration Guide Part number: R Software version: 7500-CMW710-R7178 Document version: 6W

2 Copyright 2016 Hewlett Packard Enterprise Development LP The information contained herein is subject to change without notice. The only warranties for Hewlett Packard Enterprise products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. Hewlett Packard Enterprise shall not be liable for technical or editorial errors or omissions contained herein. Confidential computer software. Valid license from Hewlett Packard Enterprise required for possession, use, or copying. Consistent with FAR and , Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor s standard commercial license. Links to third-party websites take you outside the Hewlett Packard Enterprise website. Hewlett Packard Enterprise has no control over and is not responsible for information outside the Hewlett Packard Enterprise website. Acknowledgments Intel, Itanium, Pentium, Intel Inside, and the Intel Inside logo are trademarks of Intel Corporation in the United States and other countries. Microsoft and Windows are trademarks of the Microsoft group of companies. Adobe and Acrobat are trademarks of Adobe Systems Incorporated. Java and Oracle are registered trademarks of Oracle and/or its affiliates. UNIX is a registered trademark of The Open Group.

3 Contents Multicast overview 1 Introduction to multicast 1 Information transmission techniques 1 Multicast features 3 Common notations in multicast 4 Multicast benefits and applications 4 Multicast models 4 Multicast architecture 5 Multicast addresses 5 Multicast protocols 8 Multicast packet forwarding mechanism 11 Configuring IGMP snooping 12 Overview 12 IGMP snooping ports 12 How IGMP snooping works 14 Protocols and standards 15 General configuration restrictions and guidelines 15 IGMP snooping configuration task list 16 Configuring basic IGMP snooping features 16 Enabling IGMP snooping 16 Specifying an IGMP snooping version 17 Setting the maximum number of IGMP snooping forwarding entries 18 Setting the IGMP last member query interval 18 Configuring IGMP snooping port features 19 Setting aging timers for dynamic ports 19 Configuring static ports 20 Configuring a port as a simulated member host 20 Enabling fast-leave processing 21 Disabling a port from becoming a dynamic router port 21 Configuring the IGMP snooping querier 22 Configuration prerequisites 22 Enabling the IGMP snooping querier 22 Configuring parameters for IGMP general queries and responses 23 Configuring parameters for IGMP messages 23 Configuration prerequisites 24 Configuring source IP addresses for IGMP messages 24 Setting the 802.1p priority for IGMP messages 25 Configuring IGMP snooping policies 25 Configuring a multicast group policy 25 Enabling multicast source port filtering 26 Enabling dropping unknown multicast data 27 Enabling IGMP report suppression 27 Setting the maximum number of multicast groups on a port 28 Enabling multicast group replacement 28 Displaying and maintaining IGMP snooping 29 IGMP snooping configuration examples 30 Group policy and simulated joining configuration example 30 Static port configuration example 32 IGMP snooping querier configuration example 35 Troubleshooting IGMP snooping 37 Layer 2 multicast forwarding cannot function 37 Multicast group policy does not work 38 Configuring PIM snooping 39 Overview 39 Configuring PIM snooping 40 i

4 Displaying and maintaining PIM snooping 41 PIM snooping configuration example 41 Troubleshooting PIM snooping 45 PIM snooping does not work on a Layer 2 device 45 Configuring multicast VLANs 46 Overview 46 Multicast VLAN configuration task list 48 Configuring a sub-vlan-based multicast VLAN 48 Configuration prerequisites 48 Configuration guidelines 48 Configuration procedure 48 Configuring a port-based multicast VLAN 49 Configuration prerequisites 49 Configuring user port attributes 49 Assigning user ports to a multicast VLAN 50 Setting the maximum number of multicast VLAN forwarding entries 50 Displaying and maintaining multicast VLANs 51 Multicast VLAN configuration examples 51 Sub-VLAN-based multicast VLAN configuration example 51 Port-based multicast VLAN configuration example 54 Configuring multicast routing and forwarding 58 Overview 58 RPF check mechanism 58 Static multicast routes 60 Multicast forwarding across unicast subnets 61 Configuration task list 62 Enabling IP multicast routing 62 Configuring multicast routing and forwarding 62 Configuring static multicast routes 62 Specifying the longest prefix match principle 63 Configuring multicast load splitting 63 Configuring a multicast forwarding boundary 64 Configuring static multicast MAC address entries 64 Enabling multicast forwarding between sub-vlans of a super VLAN 65 Displaying and maintaining multicast routing and forwarding 65 Multicast routing and forwarding configuration examples 67 Changing an RPF route 67 Creating an RPF route 69 Multicast forwarding over a GRE tunnel 71 Troubleshooting multicast routing and forwarding 73 Static multicast route failure 73 Configuring IGMP 75 Overview 75 IGMPv1 overview 75 IGMPv2 enhancements 76 IGMPv3 enhancements 77 IGMP SSM mapping 78 IGMP support for VPNs 79 Protocols and standards 79 IGMP configuration task list 80 Configuring basic IGMP features 80 Enabling IGMP 80 Specifying an IGMP version 81 Configuring a static group member 81 Configuring a multicast group policy 81 Adjusting IGMP performance 82 Configuring IGMP query and response parameters 82 Enabling fast-leave processing 84 Enabling IGMP NSR 85 ii

5 Configuring IGMP SSM mappings 85 Configuration prerequisites 85 Configuration procedure 85 Displaying and maintaining IGMP 85 IGMP configuration examples 86 Basic IGMP features configuration examples 86 IGMP SSM mapping configuration example 88 Troubleshooting IGMP 91 No membership information on the receiver-side router 91 Inconsistent membership information on the routers on the same subnet 92 Configuring PIM 94 Overview 94 PIM-DM overview 94 PIM-SM overview 96 BIDIR-PIM overview 100 Administrative scoping overview 103 PIM-SSM overview 105 Relationship among PIM protocols 106 PIM support for VPNs 107 Protocols and standards 107 Configuring PIM-DM 107 PIM-DM configuration task list 108 Configuration prerequisites 108 Enabling PIM-DM 108 Enabling the state refresh feature 108 Configuring state refresh parameters 109 Configuring PIM-DM graft retry timer 109 Configuring PIM-SM 110 PIM-SM configuration task list 110 Configuration prerequisites 110 Enabling PIM-SM 110 Configuring an RP 111 Configuring a BSR 112 Configuring multicast source registration 114 Configuring the switchover to SPT 115 Configuring BIDIR-PIM 115 Configuration restrictions and guidelines 115 BIDIR-PIM configuration task list 115 Configuration prerequisites 116 Enabling BIDIR-PIM 116 Configuring an RP 117 Configuring a BSR 118 Configuring PIM-SSM 120 PIM-SSM configuration task list 120 Configuration prerequisites 120 Enabling PIM-SM 121 Configuring the SSM group range 121 Configuring common PIM features 122 Configuration task list 122 Configuration prerequisites 122 Configuring a multicast source policy 122 Configuring a PIM hello policy 122 Configuring PIM hello message options 123 Configuring common PIM timers 124 Setting the maximum size of each join or prune message 126 Enabling BFD for PIM 126 Enabling PIM passive mode 126 Enabling PIM NSR 127 Displaying and maintaining PIM 127 PIM configuration examples 128 PIM-DM configuration example 128 iii

6 PIM-SM non-scoped zone configuration example 131 PIM-SM admin-scoped zone configuration example 134 BIDIR-PIM configuration example 139 PIM-SSM configuration example 143 Troubleshooting PIM 146 A multicast distribution tree cannot be correctly built 146 Multicast data is abnormally terminated on an intermediate router 147 An RP cannot join an SPT in PIM-SM 147 An RPT cannot be built or multicast source registration fails in PIM-SM 147 Configuring MSDP 149 Overview 149 How MSDP works 149 MSDP support for VPNs 154 Protocols and standards 154 MSDP configuration task list 155 Configuring basic MSDP features 155 Configuration prerequisites 155 Enabling MSDP 155 Specifying an MSDP peer 156 Configuring a static RPF peer 156 Configuring an MSDP peering connection 156 Configuration prerequisites 157 Configuring a description for an MSDP peer 157 Configuring an MSDP mesh group 157 Controlling MSDP peering connections 157 Configuring SA message-related parameters 158 Configuration prerequisites 158 Enabling multicast data encapsulation in SA messages 159 Configuring the originating RP of SA messages 159 Configuring SA request messages 159 Configuring SA message policies 160 Configuring the SA cache mechanism 161 Displaying and maintaining MSDP 161 MSDP configuration examples 162 PIM-SM inter-domain multicast configuration 162 Inter-AS multicast configuration by leveraging static RPF peers 167 Anycast RP configuration 171 SA message filtering configuration 175 Troubleshooting MSDP 178 MSDP peers stay in disabled state 178 No SA entries exist in the router's SA message cache 178 No exchange of locally registered (S, G) entries between RPs 178 Configuring multicast VPN 180 Overview 180 MD VPN overview 181 Protocols and standards 184 How MD VPN works 185 Default-MDT establishment 185 Default-MDT-based delivery 187 MDT switchover 190 Inter-AS MD VPN 191 Multicast VPN configuration task list 193 Configuring MD VPN 194 Configuration prerequisites 194 Enabling IP multicast routing in a VPN instance 194 Creating an MD for a VPN instance 195 Specifying the default-group 195 Specifying the MD source interface 195 Configuring MDT switchover parameters 196 Enabling data-group reuse logging 196 iv

7 Configuring BGP MDT 196 Configuration prerequisites 197 Enabling BGP MDT peers or peer groups 197 Configuring a BGP MDT route reflector 197 Displaying and maintaining multicast VPN 198 Multicast VPN configuration examples 199 Intra-AS MD VPN configuration example 199 MD VPN inter-as option C configuration example 212 Troubleshooting MD VPN 225 A default-mdt cannot be established 225 An MVRF cannot be created 226 Configuring MLD snooping 227 Overview 227 MLD snooping ports 227 How MLD snooping works 229 Protocols and standards 230 General configuration restrictions and guidelines 230 MLD snooping configuration task list 231 Configuring basic MLD snooping features 231 Enabling MLD snooping 231 Specifying an MLD snooping version 232 Setting the maximum number of MLD snooping forwarding entries 233 Setting the MLD last listener query interval 233 Configuring MLD snooping port features 234 Setting aging timers for dynamic ports 234 Configuring static ports 235 Configuring a port as a simulated member host 235 Enabling fast-leave processing 236 Disabling a port from becoming a dynamic router port 237 Configuring the MLD snooping querier 237 Configuration prerequisites 237 Enabling the MLD snooping querier 237 Configuring parameters for MLD general queries and responses 238 Configuring parameters for MLD messages 239 Configuration prerequisites 239 Configuring source IPv6 addresses for MLD messages 239 Setting the 802.1p priority for MLD messages 240 Configuring MLD snooping policies 241 Configuring an IPv6 multicast group policy 241 Enabling IPv6 multicast source port filtering 242 Enabling dropping unknown IPv6 multicast data 242 Enabling MLD report suppression 243 Setting the maximum number of IPv6 multicast groups on a port 243 Enabling IPv6 multicast group replacement 244 Displaying and maintaining MLD snooping 244 MLD snooping configuration examples 246 IPv6 group policy and simulated joining configuration example 246 Static port configuration example 248 MLD snooping querier configuration example 251 Troubleshooting MLD snooping 253 Layer 2 multicast forwarding cannot function 253 IPv6 multicast group policy does not work 253 Configuring IPv6 PIM snooping 255 Overview 255 Configuring IPv6 PIM snooping 256 Displaying and maintaining IPv6 PIM snooping 257 IPv6 PIM snooping configuration example 257 Troubleshooting IPv6 PIM snooping 261 IPv6 PIM snooping does not work on a Layer 2 device 261 v

8 Configuring IPv6 multicast VLANs 262 Overview 262 IPv6 multicast VLAN configuration task list 264 Configuring a sub-vlan-based IPv6 multicast VLAN 264 Configuration prerequisites 264 Configuration guidelines 264 Configuration procedure 264 Configuring a port-based IPv6 multicast VLAN 265 Configuration prerequisites 265 Configuring user port attributes 265 Assigning user ports to an IPv6 multicast VLAN 266 Setting the maximum number of IPv6 multicast VLAN forwarding entries 266 Displaying and maintaining IPv6 multicast VLANs 267 IPv6 multicast VLAN configuration examples 267 Sub-VLAN-based IPv6 multicast VLAN configuration example 267 Port-based IPv6 multicast VLAN configuration example 270 Configuring IPv6 multicast routing and forwarding 274 Overview 274 RPF check mechanism 274 IPv6 multicast forwarding across IPv6 unicast subnets 276 Configuration task list 276 Enabling IPv6 multicast routing 276 Configuring IPv6 multicast routing and forwarding 277 Specifying the longest prefix match principle 277 Configuring IPv6 multicast load splitting 277 Configuring an IPv6 multicast forwarding boundary 278 Configuring IPv6 static multicast MAC address entries 278 Enabling IPv6 multicast forwarding between sub-vlans of a super VLAN 279 Displaying and maintaining IPv6 multicast routing and forwarding 279 IPv6 multicast forwarding over a GRE tunnel configuration example 281 Network requirements 281 Configuration procedure 281 Verifying the configuration 283 Configuring MLD 284 Overview 284 How MLDv1 works 284 MLDv2 enhancements 286 MLD SSM mapping 287 MLD support for VPNs 288 Protocols and standards 288 MLD configuration task list 288 Configuring basic MLD features 288 Enabling MLD 288 Specifying an MLD version 289 Configuring a static group member 289 Configuring an IPv6 multicast group policy 290 Adjusting MLD performance 290 Configuring MLD query and response parameters 290 Enabling fast-leave processing 292 Enabling MLD NSR 292 Configuring MLD SSM mappings 293 Configuration prerequisites 293 Configuration procedure 293 Displaying and maintaining MLD 293 MLD configuration examples 294 Basic MLD features configuration example 294 MLD SSM mapping configuration example 296 Troubleshooting MLD 299 No member information exists on the receiver-side router 299 vi

9 Inconsistent membership information on the routers on the same subnet 300 Configuring IPv6 PIM 301 Overview 301 IPv6 PIM-DM overview 301 IPv6 PIM-SM overview 303 IPv6 BIDIR-PIM overview 308 IPv6 administrative scoping overview 311 IPv6 PIM-SSM overview 313 Relationship among IPv6 PIM protocols 314 IPv6 PIM support for VPNs 315 Protocols and standards 315 Configuring IPv6 PIM-DM 315 IPv6 PIM-DM configuration task list 316 Configuration prerequisites 316 Enabling IPv6 PIM-DM 316 Enabling the state refresh feature 316 Configuring state refresh parameters 317 Configuring IPv6 PIM-DM graft retry timer 317 Configuring IPv6 PIM-SM 318 IPv6 PIM-SM configuration task list 318 Configuration prerequisites 318 Enabling IPv6 PIM-SM 318 Configuring an RP 319 Configuring a BSR 320 Configuring IPv6 multicast source registration 322 Configuring the switchover to SPT 322 Configuring IPv6 BIDIR-PIM 323 Configuration restrictions and guidelines 323 IPv6 BIDIR-PIM configuration task list 323 Configuration prerequisites 323 Enabling IPv6 BIDIR-PIM 323 Configuring an RP 324 Configuring a BSR 326 Configuring IPv6 PIM-SSM 327 IPv6 PIM-SSM configuration task list 328 Configuration prerequisites 328 Enabling IPv6 PIM-SM 328 Configuring the IPv6 SSM group range 328 Configuring common IPv6 PIM features 329 Configuration task list 329 Configuration prerequisites 329 Configuring an IPv6 multicast source policy 329 Configuring an IPv6 PIM hello policy 330 Configuring IPv6 PIM hello message options 330 Configuring common IPv6 PIM timers 332 Setting the maximum size of each join or prune message 333 Enabling BFD for IPv6 PIM 333 Enabling IPv6 PIM passive mode 334 Enabling IPv6 PIM NSR 334 Displaying and maintaining IPv6 PIM 335 IPv6 PIM configuration examples 335 IPv6 PIM-DM configuration example 335 IPv6 PIM-SM non-scoped zone configuration example 338 IPv6 PIM-SM admin-scoped zone configuration example 341 IPv6 BIDIR-PIM configuration example 347 IPv6 PIM-SSM configuration example 351 Troubleshooting IPv6 PIM 354 A multicast distribution tree cannot be correctly built 354 IPv6 multicast data is abnormally terminated on an intermediate router 354 An RP cannot join an SPT in IPv6 PIM-SM 355 An RPT cannot be built or IPv6 multicast source registration fails in IPv6 PIM-SM 355 vii

10 Document conventions and icons 356 Conventions 356 Network topology icons 357 Support and other resources 358 Accessing Hewlett Packard Enterprise Support 358 Accessing updates 358 Websites 359 Customer self repair 359 Remote support 359 Documentation feedback 359 Index 361 viii

11 Multicast overview Introduction to multicast As a technique that coexists with unicast and broadcast, the multicast technique effectively addresses the issue of point-to-multipoint data transmission. By enabling high-efficiency point-to-multipoint data transmission over a network, multicast greatly saves network bandwidth and reduces network load. By using multicast technology, a network operator can easily provide bandwidth-critical and time-critical information services. These services include live webcasting, Web TV, distance learning, telemedicine, Web radio, and real-time video conferencing. Information transmission techniques Unicast The information transmission techniques include unicast, broadcast, and multicast. In unicast transmission, the information source must send a separate copy of information to each host that needs the information. Figure 1 Unicast transmission Host A Receiver Host B Source Host C Receiver Host D IP network Packets for Host B Packets for Host D Packets for Host E Receiver Host E In Figure 1, Host B, Host D, and Host E need the information. A separate transmission channel must be established from the information source to each of these hosts. In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts that need the information. If a large number of hosts need the information, the information source must send a separate copy of the same information to each of these hosts. Sending many copies can place a tremendous pressure on the information source and the network bandwidth. Unicast is not suitable for batch transmission of information. 1

12 Broadcast In broadcast transmission, the information source sends information to all hosts on the subnet, even if some hosts do not need the information. Figure 2 Broadcast transmission In Figure 2, only Host B, Host D, and Host E need the information. If the information is broadcast to the subnet, Host A and Host C also receive it. In addition to information security issues, broadcasting to hosts that do not need the information also causes traffic flooding on the same subnet. Broadcast is disadvantageous in transmitting data to specific hosts. Moreover, broadcast transmission is a significant waste of network resources. Multicast Multicast provides point-to-multipoint data transmissions with the minimum network consumption. When some hosts on the network need multicast information, the information sender, or multicast source, sends only one copy of the information. Multicast distribution trees are built through multicast routing protocols, and the packets are replicated only on nodes where the trees branch. 2

13 Figure 3 Multicast transmission The multicast source sends only one copy of the information to a multicast group. Host B, Host D, and Host E, which are information receivers, must join the multicast group. The routers on the network duplicate and forward the information based on the distribution of the group members. Finally, the information is correctly delivered to Host B, Host D, and Host E. To summarize, multicast has the following advantages: Advantages over unicast Multicast data is replicated and distributed until it flows to the farthest-possible node from the source. The increase of receiver hosts will not remarkably increase the load of the source or the usage of network resources. Advantages over broadcast Multicast data is sent only to the receivers that need it. This saves network bandwidth and enhances network security. In addition, multicast data is not confined to the same subnet. Multicast features A multicast group is a multicast receiver set identified by an IP multicast address. Hosts must join a multicast group to become members of the multicast group before they receive the multicast data addressed to that multicast group. Typically, a multicast source does not need to join a multicast group. A multicast source is an information sender. It can send data to multiple multicast groups at the same time. Multiple multicast sources can send data to the same multicast group at the same time. The group memberships are dynamic. Hosts can join or leave multicast groups at any time. Multicast groups are not subject to geographic restrictions. Multicast routers or Layer 3 multicast devices are routers or Layer 3 switches that support Layer 3 multicast. They provide multicast routing and manage multicast group memberships on stub subnets with attached group members. A multicast router itself can be a multicast group member. For a better understanding of the multicast concept, you can compare multicast transmission to the transmission of TV programs. 3

14 Table 1 Comparing TV program transmission and multicast transmission TV program transmission A TV station transmits a TV program through a channel. A user tunes the TV set to the channel. The user starts to watch the TV program transmitted by the TV station on the channel. Multicast transmission A multicast source sends multicast data to a multicast group. A receiver joins the multicast group. The receiver starts to receive the multicast data sent by the source to the multicast group. The user turns off the TV set or tunes to another channel. The receiver leaves the multicast group or joins another group. Common notations in multicast The following notations are commonly used in multicast transmission: (*, G) Rendezvous point tree (RPT), or a multicast packet that any multicast source sends to multicast group G. The asterisk (*) represents any multicast source, and "G" represents a specific multicast group. (S, G) Shortest path tree (SPT), or a multicast packet that multicast source "S" sends to multicast group "G." "S" represents a specific multicast source, and "G" represents a specific multicast group. For more information about the concepts RPT and SPT, see "Configuring PIM" and "Configuring IPv6 PIM." Multicast benefits and applications Multicast benefits Enhanced efficiency Reduces the processor load of information source servers and network devices. Optimal performance Reduces redundant traffic. Distributed application Enables point-to-multipoint applications at the price of minimum network resources. Multicast applications Multimedia and streaming applications, such as Web TV, Web radio, and real-time video/audio conferencing Communication for training and cooperative operations, such as distance learning and telemedicine Data warehouse and financial applications (stock quotes) Any other point-to-multipoint application for data distribution Multicast models Based on how the receivers treat the multicast sources, the multicast models include any-source multicast (ASM), source-filtered multicast (SFM), and source-specific multicast (SSM). 4

15 ASM model SFM model In the ASM model, any multicast sources can send information to a multicast group. Receivers can join a multicast group and get multicast information addressed to that multicast group from any multicast sources. In this model, receivers do not know the positions of the multicast sources in advance. The SFM model is derived from the ASM model. To a multicast source, the two models appear to have the same multicast membership architecture. The SFM model functionally extends the ASM model. The upper-layer software checks the source address of received multicast packets and permits or denies multicast traffic from specific sources. The receivers obtain the multicast data from only part of the multicast sources. To a receiver, multicast sources are not all valid, but are filtered. SSM model The SSM model provides a transmission service that enables multicast receivers to specify the multicast sources in which they are interested. In the SSM model, receivers have already determined the locations of the multicast sources. This is the main difference between the SSM model and the ASM model. In addition, the SSM model uses a different multicast address range than the ASM/SFM model. Dedicated multicast forwarding paths are established between receivers and the specified multicast sources. Multicast architecture IP multicast addresses the following issues: Where should the multicast source transmit information to? (Multicast addressing.) What receivers exist on the network? (Host registration.) Where is the multicast source that will provide data to the receivers? (Multicast source discovery.) How is the information transmitted to the receivers? (Multicast routing.) IP multicast is an end-to-end service. The multicast architecture involves the following parts: Addressing mechanism A multicast source sends information to a group of receivers through a multicast address. Host registration Receiver hosts can join and leave multicast groups dynamically. This mechanism is the basis for management of group memberships. Multicast routing A multicast distribution tree (a forwarding path tree for multicast data on the network) is constructed for delivering multicast data from a multicast source to receivers. Multicast applications A software system that supports multicast applications, such as video conferencing, must be installed on multicast sources and receiver hosts. The TCP/IP stack must support reception and transmission of multicast data. Multicast addresses IP multicast addresses IPv4 multicast addresses: IANA assigned the Class D address block ( to ) to IPv4 multicast. 5

16 Table 2 Class D IP address blocks and description Address block to to to Description Reserved permanent group addresses. The IP address is reserved. Other IP addresses can be used by routing protocols and for topology searching, protocol maintenance, and so on. Table 3 lists common permanent group addresses. A packet destined for an address in this block will not be forwarded beyond the local subnet regardless of the TTL value in the IP header. Globally scoped group addresses. This block includes the following types of designated group addresses: /8 SSM group addresses /8 Glop group addresses. Administratively scoped multicast addresses. These addresses are considered locally unique rather than globally unique. You can reuse them in domains administered by different organizations without causing conflicts. For more information, see RFC NOTE: Glop is a mechanism for assigning multicast addresses between different ASs. By filling an AS number into the middle two bytes of , you get 255 multicast addresses for that AS. For more information, see RFC Table 3 Common permanent multicast group addresses Address Description All systems on this subnet, including hosts and routers All multicast routers on this subnet Unassigned DVMRP routers OSPF routers OSPF designated routers and backup designated routers Shared Tree (ST) routers ST hosts RIPv2 routers Mobile agents DHCP server/relay agent All Protocol Independent Multicast (PIM) routers RSVP encapsulation All Core-Based Tree (CBT) routers Designated SBM All SBMs VRRP. IPv6 multicast addresses: 6

17 Figure 4 IPv6 multicast format The following describes the fields of an IPv6 multicast address: 0xFF The most significant eight bits are Flags The Flags field contains four bits. Figure 5 Flags field format Table 4 Flags field description Bit Description 0 Reserved, set to 0. R P T When set to 0, this address is an IPv6 multicast address without an embedded RP address. When set to 1, this address is an IPv6 multicast address with an embedded RP address. (The P and T bits must also be set to 1.) When set to 0, this address is an IPv6 multicast address not based on a unicast prefix. When set to 1, this address is an IPv6 multicast address based on a unicast prefix. (The T bit must also be set to 1.) When set to 0, this address is an IPv6 multicast address permanently-assigned by IANA. When set to 1, this address is a transient, or dynamically assigned IPv6 multicast address. Scope The Scope field contains four bits, which represent the scope of the IPv6 internetwork for which the multicast traffic is intended. Table 5 Values of the Scope field Value Meaning 0, F Reserved. 1 Interface-local scope. 2 Link-local scope. 3 Subnet-local scope. 4 Admin-local scope. 5 Site-local scope. 6, 7, 9 through D Unassigned. 8 Organization-local scope. 7

18 Value E Meaning Global scope. Group ID The Group ID field contains 112 bits. It uniquely identifies an IPv6 multicast group in the scope that the Scope field defines. Ethernet multicast MAC addresses IPv4 multicast MAC addresses: As defined by IANA, the most significant 24 bits of an IPv4 multicast MAC address are 0x01005E. Bit 25 is 0, and the other 23 bits are the least significant 23 bits of an IPv4 multicast address. Figure 6 IPv4-to-MAC address mapping The most significant four bits of an IPv4 multicast address are fixed at In an IPv4-to-MAC address mapping, five bits of the IPv4 multicast address are lost. As a result, 32 IPv4 multicast addresses are mapped to the same IPv4 multicast MAC address. A device might receive unwanted multicast data at Layer 2 processing, which needs to be filtered by the upper layer. IPv6 multicast MAC addresses: As defined by IANA, the most significant 16 bits of an IPv6 multicast MAC address are 0x3333. The least significant 32 bits are mapped from the least significant 32 bits of an IPv6 multicast address. Therefore, the problem of duplicate IPv6-to-MAC address mapping also arises like IPv4-to-MAC address mapping. Figure 7 IPv6-to-MAC address mapping Multicast protocols Multicast protocols include the following categories: Layer 3 and Layer 2 multicast protocols: Layer 3 multicast refers to IP multicast operating at the network layer. 8

19 Layer 3 multicast protocols IGMP, MLD, PIM, IPv6 PIM, MSDP, MBGP, and IPv6 MBGP. Layer 2 multicast refers to IP multicast operating at the data link layer. Layer 2 multicast protocols IGMP snooping, MLD snooping, PIM snooping, IPv6 PIM snooping, multicast VLAN, and IPv6 multicast VLAN. IPv4 and IPv6 multicast protocols: For IPv4 networks IGMP snooping, PIM snooping, multicast VLAN, IGMP, PIM, MSDP, and MBGP. For IPv6 networks MLD snooping, IPv6 PIM snooping, IPv6 multicast VLAN, MLD, IPv6 PIM, and IPv6 MBGP. This section provides only general descriptions about applications and functions of the Layer 2 and Layer 3 multicast protocols in a network. For more information about these protocols, see the related chapters. Layer 3 multicast protocols Layer 3 multicast protocols include multicast group management protocols and multicast routing protocols. Figure 8 Positions of Layer 3 multicast protocols Multicast group management protocols: Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) protocol are multicast group management protocols. Typically, they run between hosts and Layer 3 multicast devices that directly connect to the hosts to establish and maintain multicast group memberships. Multicast routing protocols: A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain multicast routes and correctly and efficiently forward multicast packets. Multicast routes constitute loop-free data transmission paths (also known as multicast distribution trees) from a data source to multiple receivers. In the ASM model, multicast routes include intra-domain routes and inter-domain routes. An intra-domain multicast routing protocol discovers multicast sources and builds multicast distribution trees within an AS to deliver multicast data to receivers. Among a variety of mature intra-domain multicast routing protocols, PIM is most widely used. Based on the forwarding mechanism, PIM has dense mode (often referred to as PIM-DM) and sparse mode (often referred to as PIM-SM). 9

20 An inter-domain multicast routing protocol is used for delivering multicast information between two ASs. So far, mature solutions include Multicast Source Discovery Protocol (MSDP) and MBGP. MSDP propagates multicast source information among different ASs. MBGP is an extension of the MP-BGP for exchanging multicast routing information among different ASs. For the SSM model, multicast routes are not divided into intra-domain routes and inter-domain routes. Because receivers know the positions of the multicast sources, channels established through PIM-SM are sufficient for the transport of multicast information. Layer 2 multicast protocols Layer 2 multicast protocols include IGMP snooping, MLD snooping, PIM snooping, IPv6 PIM snooping, multicast VLAN, and IPv6 multicast VLAN. Figure 9 Positions of Layer 2 multicast protocols IGMP snooping and MLD snooping: IGMP snooping and MLD snooping are multicast constraining mechanisms that run on Layer 2 devices. They manage and control multicast groups by monitoring and analyzing IGMP or MLD messages exchanged between the hosts and Layer 3 multicast devices. This effectively controls the flooding of multicast data in Layer 2 networks. PIM snooping and IPv6 PIM snooping: PIM snooping and IPv6 PIM snooping run on Layer 2 devices. They work with IGMP snooping or MLD snooping to analyze received PIM messages. Then, they add the ports that are interested in specific multicast data to a PIM snooping routing entry or IPv6 PIM snooping routing entry. In this way, multicast data can be forwarded to only the ports that are interested in the data. Multicast VLAN and IPv6 multicast VLAN: Multicast VLAN or IPv6 multicast VLAN runs on a Layer 2 device in a multicast network where multicast receivers for the same group exist in different VLANs. With these protocols, the Layer 3 multicast device sends only one copy of multicast to the multicast VLAN or IPv6 multicast VLAN on the Layer 2 device. This method avoids waste of network bandwidth and extra burden on the Layer 3 device. 10

21 Multicast packet forwarding mechanism In a multicast model, receiver hosts of a multicast group are usually located at different areas on the network. They are identified by the same multicast group address. To deliver multicast packets to these receivers, a multicast source encapsulates the multicast data in an IP packet with the multicast group address as the destination address. Multicast routers on the forwarding paths forward multicast packets that an incoming interface receives through multiple outgoing interfaces. Compared to a unicast model, a multicast model is more complex in the following aspects: To ensure multicast packet transmission on the network, different routing tables are used to guide multicast forwarding. These routing tables include unicast routing tables, routing tables for multicast (for example, the MBGP routing table), and static multicast routing tables. To process the same multicast information from different peers received on different interfaces, the multicast device performs an RPF check on each multicast packet. The RPF check result determines whether the packet will be forwarded or discarded. The RPF check mechanism is the basis for most multicast routing protocols to implement multicast forwarding. For more information about the RPF mechanism, see "Configuring multicast routing and forwarding" and "Configuring IPv6 multicast routing and forwarding." 11

22 Configuring IGMP snooping Overview IGMP snooping runs on a Layer 2 device as a multicast constraining mechanism to improve multicast forwarding efficiency. It creates Layer 2 multicast forwarding entries from IGMP packets that are exchanged between the hosts and the router. As shown in Figure 10, when IGMP snooping is not enabled, the Layer 2 switch floods multicast packets to all hosts in a VLAN. When IGMP snooping is enabled, the Layer 2 switch forwards multicast packets of known multicast groups to only the receivers. Figure 10 Multicast packet transmission without and with IGMP snooping IGMP snooping ports As shown in Figure 11, IGMP snooping runs on Switch A and Switch B, and Host A and Host C are receivers in a multicast group. IGMP snooping ports are divided into member ports and router ports. 12

23 Figure 11 IGMP snooping ports Router ports Member ports On an IGMP snooping Layer 2 device, the ports toward Layer 3 multicast devices are called router ports. In Figure 11, GigabitEthernet 1/0/1 of Switch A and GigabitEthernet 1/0/1 of Switch B are router ports. Router ports contain the following types: Dynamic router port When a port receives an IGMP general query whose source address is not or receives a PIM hello message, the port is added into the dynamic router port list. At the same time, an aging timer is started for the port. If the port receives either of the messages before the timer expires, the timer is reset. If the port does not receive either of the messages when the timer expires, the port is removed from the dynamic router port list. Static router port When a port is statically configured as a router port, it is added into the static router port list. The static router port does not age out, and it can be deleted only manually. Do not confuse the "router port" in IGMP snooping with the "routed interface" commonly known as the "Layer 3 interface." The router port in IGMP snooping is a Layer 2 interface. On an IGMP snooping Layer 2 device, the ports toward receiver hosts are called member ports. In Figure 11, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of Switch B are member ports. Member ports contain the following types: Dynamic member port When a port receives an IGMP report, it is added to the associated dynamic IGMP snooping forwarding entry as an outgoing interface. At the same time, an aging timer is started for the port. If the port receives an IGMP report before the timer expires, the timer is reset. If the port does not receive an IGMP report when the timer expires, the port is removed from the associated dynamic forwarding entry. Static member port When a port is statically configured as a member port, it is added to the associated static IGMP snooping forwarding entry as an outgoing interface. The static member port does not age out, and it can be deleted only manually. Unless otherwise specified, router ports and member ports in this document include both static and dynamic router ports and member ports. 13

24 How IGMP snooping works General query The ports in this section are dynamic ports. For information about how to configure and remove static ports, see "Configuring static ports." IGMP messages types include general query, IGMP report, and leave message. An IGMP snooping-enabled Layer 2 device performs differently depending on the message types. The IGMP querier periodically sends IGMP general queries to all hosts and routers on the local subnet to check for the existence of multicast group members. After receiving an IGMP general query, the Layer 2 device forwards the query to all ports in the VLAN except the receiving port. The Layer 2 device also performs one of the following actions: If the receiving port is a dynamic router port in the dynamic router port list, the Layer 2 device restarts the aging timer for the port. If the receiving port does not exist in the dynamic router port list, the Layer 2 device adds the port to the dynamic router port list. It also starts an aging timer for the port. IGMP report A host sends an IGMP report to the IGMP querier for the following purposes: Responds to queries if the host is a multicast group member. Applies for a multicast group membership. After receiving an IGMP report from a host, the Layer 2 device forwards the report through all the router ports in the VLAN. It also resolves the address of the reported multicast group, and looks up the forwarding table for a matching entry as follows: If no match is found, the Layer 2 device creates a forwarding entry with the receiving port as an outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port. If a match is found but the matching forwarding entry does not contain the receiving port, the Layer 2 device adds the receiving port to the outgoing interface list. It also marks the receiving port as a dynamic member port and starts an aging timer for the port. If a match is found and the matching forwarding entry contains the receiving port, the Layer 2 device restarts the aging timer for the port. In an application with a group policy configured on an IGMP snooping-enabled Layer 2 device, when a user requests a multicast program, the user's host initiates an IGMP report. After receiving this report, the Layer 2 device resolves the multicast group address in the report and performs ACL filtering on the report. If the report passes ACL filtering, the Layer 2 device creates an IGMP snooping forwarding entry for the multicast group with the receiving port as an outgoing interface. If the report does not pass ACL filtering, the Layer 2 device drops this report. The multicast data for the multicast group is not sent to this port, and the user cannot retrieve the program. Leave message A Layer 2 device does not forward an IGMP report through a non-router port because of the host IGMP report suppression mechanism. For more information about the mechanism, see "Configuring IGMP." An IGMPv1 receiver host does not send any leave messages when it leaves a multicast group. The Layer 2 device cannot immediately update the status of the port that connects to the receiver host. The Layer 2 device does not remove the port from the outgoing interface list in the associated forwarding entry until the aging time for the group expires. An IGMPv2 or IGMPv3 host sends an IGMP leave message when it leaves a multicast group. When the Layer 2 device receives an IGMP leave message on a dynamic member port, the Layer 2 device first examines whether a forwarding entry matches the group address in the message. 14

25 If no match is found, the Layer 2 device discards the IGMP leave message. If a match is found but the receiving port is not an outgoing interface in the forwarding entry, the Layer 2 device discards the IGMP leave message. If a match is found and the receiving port is not the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions: Discards the IGMP leave message. Sends an IGMP group-specific query to identify whether the group has active receivers attached to the receiving port. Sets the aging timer for the receiving port to twice the IGMP last member query interval. If a match is found and the receiving port is the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions: Forwards the IGMP leave message to all router ports in the VLAN. Sends an IGMP group-specific query to identify whether the group has active receivers attached to the receiving port. Sets the aging timer for the receiving port to twice the IGMP last member query interval. After receiving the IGMP leave message on a port, the IGMP querier resolves the multicast group address in the message. Then, it sends an IGMP group-specific query to the multicast group through the receiving port. After receiving the IGMP group-specific query, the Layer 2 device forwards the query through all its router ports in the VLAN and all member ports of the multicast group. Then, it waits for the responding IGMP report from the directly connected hosts. For the dynamic member port that received the leave message, the Layer 2 device also performs one of the following actions: If the port receives an IGMP report before the aging timer expires, the Layer 2 device resets the aging timer. If the port does not receive an IGMP report when the aging timer expires, the Layer 2 device removes the port from the forwarding entry for the multicast group. Protocols and standards RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches General configuration restrictions and guidelines When you configure IGMP snooping, follow these restrictions and guidelines: For a VLAN configured with IGMP snooping, if you change the VPN instance bound to the VLAN interface, Layer 2 multicast traffic for the VLAN is interrupted. In this case, you must execute the reset igmp-snooping group command so that new IGMP snooping forwarding entries can be created. For IGMP reports received from secondary VLANs, the relevant IGMP snooping forwarding entries are maintained by the primary VLAN. Therefore, you need to configure IGMP snooping only for the primary VLAN. The IGMP snooping configuration made for secondary VLANs does not take effect. For more information about primary VLANs and secondary VLANs, see Layer 2 LAN Switching Configuration Guide. The IGMP snooping configurations made on Layer 2 aggregate interfaces do not interfere with the configurations made on member ports. In addition, the configurations made on Layer 2 aggregate interfaces do not take part in aggregation calculations. The configuration made on a member port of the aggregate group takes effect after the port leaves the aggregate group. 15

26 IGMP snooping configuration task list Tasks at a glance Configuring basic IGMP snooping features: (Required.) Enabling IGMP snooping (Optional.) Specifying an IGMP snooping version (Optional.) Setting the maximum number of IGMP snooping forwarding entries (Optional.) Setting the IGMP last member query interval Configuring IGMP snooping port features: (Optional.) Setting aging timers for dynamic ports (Optional.) Configuring static ports (Optional.) Configuring a port as a simulated member host (Optional.) Enabling fast-leave processing (Optional.) Disabling a port from becoming a dynamic router port Configuring the IGMP snooping querier: (Optional.) Enabling the IGMP snooping querier (Optional.) Configuring parameters for IGMP general queries and responses Configuring parameters for IGMP messages: (Optional.) Configuring source IP addresses for IGMP messages (Optional.) Setting the 802.1p priority for IGMP messages Configuring IGMP snooping policies: (Optional.) Configuring a multicast group policy (Optional.) Enabling multicast source port filtering (Optional.) Enabling dropping unknown multicast data (Optional.) Enabling IGMP report suppression (Optional.) Setting the maximum number of multicast groups on a port (Optional.) Enabling multicast group replacement Configuring basic IGMP snooping features Before you configure basic IGMP snooping features, complete the following tasks: Configure VLANs. Determine the IGMP snooping version. Determine the maximum number of IGMP snooping forwarding entries. Determine the IGMP last member query interval. Enabling IGMP snooping When you enable IGMP snooping, follow these guidelines: You must enable IGMP snooping globally before you enable it for a VLAN. IGMP snooping configuration made in VLAN view takes effect only on the member ports in that VLAN. You can enable IGMP snooping for the specified VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN view has the same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect. 16

27 Enabling IGMP snooping for the specified VLANs Step Command Remarks 1. Enter system view. system-view N/A 2. Enable IGMP snooping globally and enter IGMP-snooping view. 3. Enable IGMP snooping for the specified VLANs. igmp-snooping enable vlan vlan-list By default, IGMP snooping is globally disabled. By default, IGMP snooping is disabled for a VLAN. Enabling IGMP snooping for a VLAN Step Command Remarks 1. Enter system view. system-view N/A 2. Enable IGMP snooping globally and enter IGMP-snooping view. igmp-snooping By default, IGMP snooping is disabled. 3. Return to system view. quit N/A 4. Enter VLAN view. vlan vlan-id N/A 5. Enable IGMP snooping for the VLAN. igmp-snooping enable By default, IGMP snooping is disabled in a VLAN. Specifying an IGMP snooping version Different IGMP snooping versions process different versions of IGMP messages. IGMPv2 snooping processes IGMPv1 and IGMPv2 messages, but it floods IGMPv3 messages in the VLAN instead of processing them. IGMPv3 snooping processes IGMPv1, IGMPv2, and IGMPv3 messages. If you change IGMPv3 snooping to IGMPv2 snooping, the switch does the following: Clears all IGMP snooping forwarding entries that are dynamically added. Keeps static IGMPv3 snooping forwarding entries (*, G). Clears static IGMPv3 snooping forwarding entries (S, G), which will be restored when IGMP snooping is switched back to IGMPv3 snooping. For more information about static IGMP snooping forwarding entries, see "Configuring static ports." You can specify the version for the specified VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN view has the same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect. Specifying an IGMP snooping version for the specified VLANs Step Command Remarks 1. Enter system view. system-view N/A 2. Enable IGMP snooping globally and enter IGMP-snooping view. 3. Specify an IGMP snooping version for the specified igmp-snooping version version-number vlan vlan-list N/A The default setting is 2. 17